Batteries, such as primary alkaline batteries, are commonly used as energy sources. Generally, alkaline batteries include a cathode, an anode, a separator, and an electrolytic solution. The cathode can include, for example, manganese dioxide particles as the active material, carbon particles that enhance the conductivity of the cathode, and a binder. The anode may be, for example, a gel including zinc particles as the active material. The separator is disposed between the cathode and the anode. The electrolytic solution can be, for example, a hydroxide solution that is dispersed throughout the battery.
It is desirable for a primary alkaline battery to have a high discharge capacity. One factor that affects the discharge capacity is the quantity of manganese dioxide in the cathode. As a general rule, the more manganese dioxide in the cathode, the higher the discharge capacity of the battery. But the cathode must also include a sufficient quantity of carbon particles for adequate conductivity. Thus, the quantity of manganese dioxide that can be included in the cathode is limited in part by the quantity of carbon particles required for adequate conductivity.
Typically, the carbon particles used in cathode are composed of graphite. It is known to use a specific type of graphite known as expanded graphite in place of normal graphite particles in the cathode. Expanded graphite is a flake graphite that is chemically treated and heated at a high temperature resulting in the exfoliation of the graphite particles. This produces a graphite with a significantly higher surface area thereby providing better contact with the manganese dioxide particles in the cathode. As a result, a quantity of expanded graphite particles provides a higher degree of conductivity to the cathode than the same quantity of non-expanded graphite particles. This in turn means that less graphite and more manganese dioxide can be included in the cathode, thus increasing the discharge capacity of the battery.